Methods of extrusion and wiredrawing of metallic products and devices for the practical application of said improved methods



Dec. 27, 1966 Y TERRAS 3,293,899

METHODS OF EXTRUSION AND WIREDRAWING 0F METALLIC PRODUCTS AND DEVICES FOR THE PRACTICAL APPLICATION OF SAID IMPROVED METHODS Filed Oct. 17, 1963 2 Sheets-Sheet l l "A F|G.|

4 rrqeye Y5 Dec. 27, 1966 Y. TERRAS 3,293,899

METHODS OF EXTRUSION AND WIREDRAWING OF METALLIC PRODUCTS AND DEVICES FOR THE PRACTICAL APPLICATION OF SAID IMPROVED METHODS Filed Oct. 17, 1963 2 Sheets-Sheet 2 FIG.5

FIG.7

FIG.8

IN VE/V TOE Yv s The/m5 TTQRN United States Patent C) M 5 Claims. (c1. 72-364) The present invention relates to methods of extrusion and wiredrawing of metallic products, especially of precious metals and alloys and to devices for the practical application of said improved methods.

The invention is more especially concerned with improvements in the conventional methods of extrusion wherein a cylinder of metal or metal alloy technically known as a slug is in the majority of cases previously heated then forced through an opening known as a die under the action of pressure, usually hydraulic pressure exerted by an assembly which is referred to as an extruding press. The cross-sectional area of said opening is necessarily limited to a value such that the available pressure is higher than the pressure which is necessary for the purpose of processing the metal or metal alloy through the die; and the ratio of the cross-sectional area of the slug to the cross-sectional area of the die, referred to as the extrusion ratio, is limited by the nature of the metal or metal alloy to be extruded.

The invention is also concerned with improvements in conventional methods of wiredrawing wherein a wire of metal or metal alloy is drawn through a series of dies which successively diminish in diameter, with the result that the cross-section of said wire is gradually reduced to that of the last hole through which it is drawn, means for heating said wire being provided if necessary either prior to insertion through the first die or between each die.

The primary object of the present invention is to make the above-mentioned conventional methods such that they meet the various practical requirements more effectively than has hitherto been possible, this object being achieved by artificially increasing the extrusion or drawing ratio and in particular by offering the following principal advantages:

(a) An improvement in the quality of the extruded product by eliminating the repeated operations of annealing and pickling which produce a surface change in the composition of metal alloys;

(b) An increase in the value of the extruded product in inverse ratio to the cross-sectional area of said product, without reduction in the hourly tonnage produced by the extruding press;

(c) The formation in the extruded material of a structure which very substantially improves the cold wiredrawing characteristics;

(d) The possibility of fabricating in a conventional extruding press end products of small size made from materials which cannot be worked in the cold state;

(e) The possibility of extruding the same material to variable diameters in a single pass;

(f) The possibility of reaching very high winding speeds;

(g) The elimination of wiredrawing dies and the lubrication which their presence made necessary;

(h) The possibility of wiredrawing of materials which do not admit of being formed in the cold state;

(i) The possibility of obtaining elongation values of 400% per drawing pass;

3,Z%,899 Patented Dec. 27, 1966 (j) The wear of tools reduced to practically nothing on account of the increase in cross-section of the extrusion die.

The invention mainly consists in subjecting a metallic wire, especially as said wire passes out of the die, to a controlled elongation produced by suitable means in such a manner that the final diameter of the wire is smaller than the initial diameter thereof, heating means being additionally provided during the operation as well as means which may be required for the purposeof cooling either by liquids or gases especially with the aid of cooling baths or blowing in order to interrupt said elongation at will.

Apart from this main feature, the invention consists of certain other features of the process which are preferably employed at the same time, namely:

The controlled elongation is achieved by applying a tractive force on the metallic wire between the die and a winding drum, said tractive force being exerted downwards by the weight of the wire which may further be increased by the weight of a loaded pulley or upwards by a set of two pulleys and a balance weight;

The said controlled elongation is achieved as a result of differences in speed between the outlet of the die or a capstan and a winding drum, a caterpillar drawing machine or capstan, means being additionally provided for measuring these different speeds and the different diameters of the wire;

The said controlled elongation is achieved as a result of differences in speed between successive capstans to which are imparted increasingspeeds of rotation and a final winding drum, heating means being additionally provided between said capstans.

The invention also consists of a device for the practical application of the method, said device comprising a conventional extruding press equipped with a ram designed for operation at a speed which can be maintained constant, a suitably lubricated die and a winch equipped with a motor and speed-changing mechanism, a clutch with or without adjustable slip, a mechanical brake and retractable winding drum, characterized in that means are provided for measuring at each moment the diameter of the wire which is obtained as well as the speed of the ram and of the winding drum, additional means being provided .for maintaining the speed of the winding drum at a higher value than the speed of delivery from the die, provision being made for controlling the difference between said speeds in dependence on the momentary diameter of said Wire, either one ora number of intermediate capstans being additionally provided between the delivery side of said die and said winding drum.

The invention finally consists in a certain number of additional arrangements'which are preferably employed at the same time as the device referred to above, namely:

The means for measuring the speeds of the ram and of the winding drum are tacho-generators with receivers;

The means for measuring the speeds of the ram and of the winding dr-um are electronic tachometers;

The means for measuring the diameter of the wire is an electronic micrometer which is placed over said wire at the input of the winding drum.

A better understanding of the invention will in any case be gained from the complementary description which follows below as well as from the accompanying drawings, it being understood that said complementary description and drawings are given solely by way of indication and not in any limiting sense.

In the accompanying drawings, FIGS. 1 and 2 are diagrammatic views taken in elevation and in plan of an arrangement which permits the weight of the wire to carry out the controlled elongation process;

FIG. 3 is a diagram of an arrangement in which provision is made for a balance weight;

FIGS. 4 and 5 are diagrams of two arrangements with intermediate capstan;

FIG. 6 is a diagram of an arrangement without intermediate capstan wherein provision is made for stopping the elongation process by means of a gas blast;

FIG. 7 is a diagram of an arrangement wherein use is made of liquid baths, caterpillar-type drawing machine and rotary barrel;

FIG. 8 is a diagram of a wiredrawing arrangement.

As shown in FIGS. 1 and 2, the use of gravity as a constant tractive force is a method which can readily be applied to the process according to the invention.

An extruding press 1 is fitted with a die 2 through which is forced a wire 3, said wire being then wound on a winding drum 4 to which is imparted a movement of rotation. The winding drum 4 has not been set opposite the die 2 but has been displaced through an angle a relative to the direction of said die. The axis of said winding drum is located at the distance D from the die. This arrangement, which allows the weight of the wire 3 to produce an action between the die 2 and the winding drum 4, is unusual inasmuch as it had hitherto been customary in extrusion processes of the prior art to allow the wire to snake over a large table located in front of the extruding press. It is accordingly found that, under the action of the tractive force applied by the weight of the wire 3, said wire is elongated while being reduced in diameter, thereby making it necessary to ensure that the speed of rotation of the winding drum is higher than the speed at which the wire passes out of the die.

Tests have been carried out in which sluggs of metal alloy 120 millimeters in diameter and 420 millimeters in length were employed as starting material and forced through a die having a hole diameter of 3 mm. The winding device consisted of a reel driven at variable speed from a reduction-gear motor equipped with a clutch with variable slip adjustable during operation. In the case of the extrusion process which was then performed, the distance D was 10 meters and the angle at was approximately The diameter of the wire thus obtained was not 3 millimeters but 2.7 millimeters and the wire had been subjected to an elongation of the order of 23% as a result of the action of gravity.

By causing the distance D and the angle a to vary, it is possible either to increase or reduce the tractive force applied on the wire. However, two simple devices make it possible to increase said tractive force even if D and or remain constant.

The first of the aforesaid devices, not shown in the drawings, can simply consist of a pulley which is rotatably mounted on a pin and suspended from the wire during the extrusion process after the fashion of a cable car. A suitable weight can be suspended from said pulley.

The second of the aforesaid devices as shown in FIG. 3 can consist of a pulley 5 which draws the wire 3 upwards by means of a balance weight 6 through the intermediary of a second pulley 7. The extruding press 1, the die 2 and the winding drum 4 remain similar to those employed in the preceding cases. This second device, which is derived from the first, provides a more practical system of operation. When controlling the slippage of the clutch of the winding drum 4, it is merely necessary for the operator to perform the relatively simple task of maintaining the pulley 5 between position 5a and position 5b.

A constant pull can also be obtained by means of a capstan, as shown in FIG. 4. The wire 3 passes out of the extruding press 1 through the die 2, is then wound three or four times around the capstan 8 to which is appliedby means of an electric device (for example by means of eddy currents) ormechanical device such as a friction drive or by means of an electromechanical or hydraulic device-a constant torque 9 which transmits a constant pull on the wire 3. The said wire is wound on a winding drum 4 of ordinary type as soon as it has passed off the capstan 8.

FIG. 5 shows an alternative form of the arrangement hereinbefore described but the operation of which is more intricate. As the wire 3 passes out of the extruding press 1 through the die 2, said wire is pulled only by the winding drum 4 and is no longer pulled by the capstan. By means of the same devices as those which have been described in the foregoing embodiments, the capstan 10 accordingly applies a load torque when set in rotation by the winding drum 4, said load torque producing a constant pull in the direction opposite to that of the system of assembly which has been previously described.

The solution which appears to give the best results, however, consists in dispensing with a capstan altogether, which accordingly results in the particularly simple arrangement shown in FIG. 6. The wire 3 passes out of the extruding press 1 through the die 2 at a speed V and is then wound on the drum 4 at a speed V which is higher than V If the diameter of the die hole is' designated by the reference d and the diameter of the wire which is wound on the drum 4 is designated by the reference d the characteristic principle of the extrusion process in accordance with the invention can be expressed by the equation:

The diameter d being of course already known, it is merely necessary to determine V by means of the speed of displacement of the ram as measured by a tachometer, to measure V by means of a tacho-generator which is associated with the winding drum 4 and to keep constant watch and control over the diameter d of the wire which is obtained with the aid of an electronic micrometer which is placed over the wire at the input of the winding drum 4.

In order to ensure effective operation of this method, the extruding press 1 must, however, satisfy certain requirements. The press which was employed in the process referred to above was a hydraulic press and comprised two separate circuits (slow-fast) which provided speeds ranging from 500 meters in less than one second to 500 meters in more than ten minutes. The operation of the rolling gate was extremely smooth and easy to control with a really instantaneous response time.

The winch section, that is to say the combined assembly of installations which follow the die, consisted of the following essential components:

a 15 H.P. AC. motor,

a speed-changer providing a ratio of 1 to 6 operated from the press,

a clutch adapted to operate with or without controlled slippage operated by the winch section operator,

a tacho-generator,

a mechanical brake,

a retractable winding drum 600 millimeters in diameter to which is imparted a speed which can be varied from to 600 meters per minute.

The procedure involved in the operation which is represented diagrammatically in FIG. 6 can be as follows: after passing out of the press 2, the wire 3 is immediately engaged over the winding drum 4. The operator who is stationed at the control desk progressively accelerates up to the appropriate speed while interpreting the indications of the ram tachometer. At the same time, the operator who is stationed at the winch section progressively lets in the clutch. In less than six to eight seconds, the electronic micrometer which is placed over the wire is set into operation with the result that the diameter of said wire will thereafter be maintained constant. The said electronic micrometer is in fact the only instrument of the installation which indicates in a continuous manner any possible variation in the cross-sectional area of the die during the extrusion process, that is to say either an increase in cross-section as a result of wear or a reduction in cross-section due to creep of the steel.

Any of the above-mentioned variations which are liable to occur are corrected either :by actuating the rolling gate or by modifying the winding speed. The speed of the winding drum 4 is practically constant while the speed of the ram is maintained constant by actuating the control lever of the rolling gate. The thickness of the coiled wire can be accurate to within 10.05 mm. in respect of a diameter of 1.40 mm., for example. When the extrusion process is completed, great care must be taken to ensure that the winding drum 4 is not braked rapidly, thereby permitting the formation of narrowed ends for drawing. This precaution makes it possible to insert the ends through the first three die-holes when subsequently performing any wiredrawing operation. Of course, this method of extrusion calls for close co-operation between the operator who is stationed at the control desk of the press section and the operator who is stationed at the control desk of the winch section but very good results can thus be achieved after only a little training.

As will be readily understood, provision can be made for the automation of this operation, either by maintaining constant the speed of translation of the ram while the speed of the winding drum 4 is controlled in accordance with the measurement of the diameter of the wire which is obtained or alternatively by controlling both the translational motion of the ram and the speed of the winding drum in dependence on the measurement of said diameter.

There will now be given below various examples of extrusion operations as performed in accordance with FIG. 6, the gas blown being air.

Example 1.Extrusion of an alloy containing 150 parts per thousand of silver, 50 parts per thousand of phosphorus and 800 parts per thousand of copper, said alloy being employed in particular as hard solder for brazing copper:

Speed of wind- Wire diameters Diameter 01 the die-hole ing drum, obtained meters/min.

Cold wiredrawing of such an alloy cannot be effected if the extrusion of this latter has not been performed in in accordance with the process of the invention.

Example 2.-Extrusi-on of an alloy containing 480 parts per thousand of silver, 150 parts per thousand of copper, 270 parts per thousand of zinc and 100 parts per thousand of cadmium, said alloy being employed as a high-strength compound for brazing steel parts:

Diameter of die-hole mm 3.50 Speed of winding dru-m meters/min 415 Diameter obtained 1.40/ 1.50

Diameter of die-hole mm 4.50 Speed of winding drum meters/min 370 Diameter obtained 1.8/ 1.9

It should be noted that the extrusion process in 'accordance with the method of the invention can be carried out through die-plates having a number of holes. The said process can also be put to use in the case of bars or structural shapes, the winding drum being in that case replaced by a conventional drawing bench which is not equipped with any die-plate but which is fitted with a tachometer or caterpillar drawing machine. As shown in FIG. 7, the wire 3 which passes out of the extruding press 1 through the die 2 is stretched by -a caterpillar drawing machine 11 at the output end of which the wire can be either deposited inside a barrel 12 to which is imparted a movement of rotation or alternatively cut into straight rods by means of conventional flying shears, not shown in the drawings. The controlled elongation of the wire 3 can be stopped at any desired point by causing said wire to pass through an acid bath 13 which can be followed by a rinsing-water bath 14. The presence of a liquid necessarily means that the elongation of the wire 3 is stopped almost instantaneously, and it will naturally be understood that this means can be employed in any one of the preceding arrangements.

Finally, the method in accordance with the invention produces particularly advantageous results in the case of materials which are subjected to a wiredrawing process Without dies and which would otherwise not be drawab-le or would in any case require a large number of successive dies. As can be seen in FIG. 8, one wiredrawing arrangement consists of a series of capstans 15, 16, 17, for example, which are provided in suitable number and to which are imparted increasing speeds of rotation respectively V V V Between said capstans, provision can be made for heat sources such as the sources 18 and 19 and the wire 3 which passes out of the last capstan, for example the capstan 17, can either be wound on a horizontal reel 20 or a vertical reel 21 to which is imparted a speed V or V either equal to or higher than the speed V or alternatively fall into a rotary barrel, or else be drawn by a caterpillar drawing machine and cut into straight rods of desired length (devices not shown in the drawings). It can readily be understood that, between any two capstans, the wire is subjected to a tractive force and consequently to an elongation which is greater as the difference in speeds of said two capstans is greater; conversely, if a certain pull is exerted on the wire 3 as this latter passes off one of the capstans, the following capstan will accordingly rotate at a speed which is higher than that of the capstan previously considered. It is thus possible to carry out the wiredrawing of alloys which do not permit of cold forming, also to obtain elongations of 400% and over per pass, and finally to operate at very high speeds; wiredrawing dies are thus dispensed with, together with the heat treatments which were made necessary by the work hardening of products. Wear of the equipment represented in FIG. 8 is practically zero.

The method in accordance with the present invention and the various modes of practical operation thereof provide the possibility of obtaining at will a wire which is reduced to the requisite diameter and at very high winding or cutting speeds. If it is recalled that, in the case of certain materials, there exists a critical extrusion speed which is independent of the extrusion ratio, the .present invention which permits of reasonable extrusion speeds using dies of substantial cross-section while maintaining high winding speeds is accordingly all the more advantageous inasmuch as it permits a considerably higher hourly tonnage of a product which has a much smaller diameter and which by any other method of the prior art would be more costly to produce.

It will be understood that the invention is not limited to those examples of construction or modes of application which have been described and illustrated but is intended, on the contrary, to include within its scope all alternative forms.

What I claim is:

1. A method of extruding and wiredrawing a metallic product for controlled elongation thereof to produce a corresponding controlled reduction in the diameter thereof, said method comprising the steps of extruding said product, applying a tractive force to said product at a point spaced from the point of extrusion, applying heat to said products between said points, and selectively applying cold thereto to interrupt said elongation.

2. A method of extrusion and wiredrawing in accordance with claim 1 wherein said product is a metallic wire and wherein said controlled elongation is achieved by applying a tractive force on said metallic wire between said die orifice and a winding station, said tractive force being exerted downward at least in part by the weight of the wire being drawn.

3. A method of extrusion and wiredrawing in accordance with claim 1 wherein said product is a metallic wire and wherein said controlled elongation is achieved by applying a tractive force on said metallic wire between said die orifice and a winding station, said tractive force being exerted upward against the wire being drawn.

4. A method of extrusion in accordance with claim 1 wherein said controlled elongation is effected by measuring and controlling the rate of extrusion at said die orifice and by simultaneously withdrawing the product being drawn at a point spaced from said die orifice, the rate of withdrawal being a measured and controlled rate less than the rate of extrusion to thereby control the amount of elongation of the product.

5. A method of extrusion and wiredrawing in accordance with claim 4 wherein successive forces of withdrawal are applied at spaced points along the length of the product being drawn and at successively increasing rates of speed and wherein heat is applied between each application of said withdrawal forces.

References Cited by the Examiner UNITED STATES PATENTS 551,306 12/1895 Converse 207-12 2,569,264 9/1951 Stone so 35 2,893,552 7/1959 Davies 207-12 2,914,170 11/1959 Kent 207-1.2

CHARLES W. LANHAM, Primary Examiner.

20 H. D. HOINKES, Assistant Examiner. 

1. A METHOD OF EXTRUDING AND WIRE DRAWING A METALLIC PRODUCT FOR CONTROLLED ELONGATION THEREOF TO PRODUCE A CORRESPONDING CONTROLLED REDUCTION IN THE DIAMTER THEREOF, SAID METHOD COMPRISING THE STEPS OF EXTRUDING SAID PRODUCT, APPLYING A TRACTIVE FORCE TO SAID PRODUCT AT A POINT SPACED FROM THE POINT OF EXTRUSION, APPLYING HEAT TO SAID PRODUCTS BETWEEN SAID POINTS, AND SELECTIVELY APPLYING COLD THERETO TO INTERRUPT SAID ELONGATION. 